Improve retries for sync client. (#2377)

pymodbus/client/base.py

@@ -108,9 +108,6 @@ async def async_execute(self, request) -> ModbusResponse:
             async with self._lock:
                 req = self.build_response(request)
                 self.ctx.send(packet)
-                if not request.slave_id:
-                    resp = None
-                    break
                 try:
                     resp = await asyncio.wait_for(
                         req, timeout=self.ctx.comm_params.timeout_connect
@@ -124,7 +121,7 @@ async def async_execute(self, request) -> ModbusResponse:
                 f"ERROR: No response received after {self.retries} retries"
             )
 
-        return resp  # type: ignore[return-value]
+        return resp
 
     def build_response(self, request: ModbusRequest):
         """Return a deferred response for the current request.

pymodbus/client/serial.py

@@ -37,7 +37,7 @@ class AsyncModbusSerialClient(ModbusBaseClient):
     :param name: Set communication name, used in logging
     :param reconnect_delay: Minimum delay in seconds.milliseconds before reconnecting.
     :param reconnect_delay_max: Maximum delay in seconds.milliseconds before reconnecting.
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
     :param on_connect_callback: Function that will be called just before a connection attempt.
 
@@ -121,7 +121,7 @@ class ModbusSerialClient(ModbusBaseSyncClient):
     :param name: Set communication name, used in logging
     :param reconnect_delay: Not used in the sync client
     :param reconnect_delay_max: Not used in the sync client
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
 
     Note that unlike the async client, the sync client does not perform

pymodbus/client/tcp.py

@@ -28,7 +28,7 @@ class AsyncModbusTcpClient(ModbusBaseClient):
     :param source_address: source address of client
     :param reconnect_delay: Minimum delay in seconds.milliseconds before reconnecting.
     :param reconnect_delay_max: Maximum delay in seconds.milliseconds before reconnecting.
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
     :param on_connect_callback: Function that will be called just before a connection attempt.
 
@@ -99,7 +99,7 @@ class ModbusTcpClient(ModbusBaseSyncClient):
     :param source_address: source address of client
     :param reconnect_delay: Not used in the sync client
     :param reconnect_delay_max: Not used in the sync client
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
 
     .. tip::

pymodbus/client/tls.py

@@ -27,7 +27,7 @@ class AsyncModbusTlsClient(AsyncModbusTcpClient):
     :param source_address: Source address of client
     :param reconnect_delay: Minimum delay in seconds.milliseconds before reconnecting.
     :param reconnect_delay_max: Maximum delay in seconds.milliseconds before reconnecting.
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
     :param on_connect_callback: Function that will be called just before a connection attempt.
 
@@ -122,7 +122,7 @@ class ModbusTlsClient(ModbusTcpClient):
     :param source_address: Source address of client
     :param reconnect_delay: Not used in the sync client
     :param reconnect_delay_max: Not used in the sync client
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
 
     .. tip::

pymodbus/client/udp.py

@@ -30,7 +30,7 @@ class AsyncModbusUdpClient(ModbusBaseClient):
     :param source_address: source address of client,
     :param reconnect_delay: Minimum delay in seconds.milliseconds before reconnecting.
     :param reconnect_delay_max: Maximum delay in seconds.milliseconds before reconnecting.
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
     :param on_connect_callback: Function that will be called just before a connection attempt.
 
@@ -101,7 +101,7 @@ class ModbusUdpClient(ModbusBaseSyncClient):
     :param source_address: source address of client,
     :param reconnect_delay: Not used in the sync client
     :param reconnect_delay_max: Not used in the sync client
-    :param timeout: Timeout for a connection request, in seconds.
+    :param timeout: Timeout for connecting and receiving data, in seconds.
     :param retries: Max number of retries per request.
 
     .. tip::

pymodbus/transaction.py

@@ -8,6 +8,7 @@
 ]
 
 import struct
+import time
 from contextlib import suppress
 from threading import RLock
 from typing import TYPE_CHECKING
@@ -387,11 +388,21 @@ def _recv(self, expected_response_length, full) -> bytes:  # noqa: C901
                     total = expected_response_length + min_size
             else:
                 total = expected_response_length
+            retries = 0
+            missing_len = expected_response_length
+            result = read_min
+            while missing_len and retries < self.retries:
+                if retries:
+                    time.sleep(0.1)
+                data = self.client.recv(expected_response_length)
+                result += data
+                missing_len -= len(data)
+                retries += 1
         else:
             read_min = b""
             total = expected_response_length
-        result = self.client.recv(expected_response_length)
-        result = read_min + result
+            result = self.client.recv(expected_response_length)
+            result = read_min + result
         actual = len(result)
         if total is not None and actual != total:
             msg_start = "Incomplete message" if actual else "No response"

test/conftest.py

@@ -287,17 +287,7 @@ def recv(self, size):
         """Receive."""
         if not self.packets or not size:
             return b""
-        # if not self.buffer:
-        #    self.buffer = self.packets.popleft()
-        # if size >= len(self.buffer):
-        #     retval = self.buffer
-        #     self.buffer = None
-        # else:
-        #     retval = self.buffer[0:size]
-        #    self.buffer = self.buffer[size]
-        self.buffer = self.packets.popleft()
-        retval = self.buffer
-        self.buffer = None
+        retval = self.packets.popleft()
         self.in_waiting -= len(retval)
         return retval
 
@@ -309,6 +299,10 @@ def recvfrom(self, size):
         """Receive from."""
         return [self.recv(size)]
 
+    def write(self, msg):
+        """Write."""
+        return self.send(msg)
+
     def send(self, msg):
         """Send."""
         if not self.copy_send:

test/sub_client/test_client_sync.py

@@ -422,6 +422,21 @@ def test_serial_client_recv(self):
         client.socket.timeout = 0
         assert client.recv(0) == b""
 
+    def test_serial_client_recv_split(self):
+        """Test the serial client receive method."""
+        client = ModbusSerialClient("/dev/null")
+        with pytest.raises(ConnectionException):
+            client.recv(1024)
+        client.socket = mockSocket(copy_send=False)
+        client.socket.mock_prepare_receive(b'')
+        client.socket.mock_prepare_receive(b'\x11\x03\x06\xAE')
+        client.socket.mock_prepare_receive(b'\x41\x56\x52\x43\x40\x49')
+        client.socket.mock_prepare_receive(b'\xAD')
+        reply_ok = client.read_input_registers(0x820, 3, slave=17)
+        assert not reply_ok.isError()
+        client.close()
+
+
     def test_serial_client_repr(self):
         """Test serial client."""
         client = ModbusSerialClient("/dev/null")